Effect Of Fertilization Depth On Light Energy Utilization And Yield Of Winter Wheat Under Different Simulated Precipitations

The deep placement of fertilizer can effectively reduce the loss of fertilizer nutrients in the early stage and improve crop yield.At present,it is not clear about the effect of fertilizer application depth on light energy utilization and nitrogen nutrient utilization in winter wheat under different precipitation year types.In this study,three precipitation year types(dry year=125 mm,T1;normal year=200 mm,T2;wet year=275 mm,T3)and four fertilizer depth treatments(D5:5 cm,conventional fertilizer depth,D15:15 cm,D25:25 cm,and D35:35cm)were applied to winter wheat during the fertility period of 2020-2022 to investigate the effects of fertilizer application depth under different rainfall on winter wheat growth,canopy light energy interception capacity,leaf source functional characteristics,nutrient uptake and utilization,and yield and its components.To investigate the regulatory effect of fertilizer application depth on light energy utilization and yield of winter wheat,and to provide theoretical reference for optimizing the management technology of fertilizer application for yield increase of winter wheat.The main findings were as follows.(1)Under T1 precipitation type,deep fertilizer application significantly increased relative chlorophyll content(SPAD)8.10%-13.11%,net photosynthetic rate(Pn)6.92%-17.15%,transpiration rate(Tr)8.78%-20.62%,stomatal conductance(Gs)7.49%-21.08%,photosystem II potential activity(Fv/Fo)in winter wheat leaves compared with conventional fertilizer application 4.02%-13.36%,maximum photosystem II photochemical efficiency(Fv/Fm)5.02%-9.01%,actual photochemical efficiency(Φps II)4.56%-9.58%,electron transfer rate(ETR)4.15%-6.53%and significantly reduced intercellular CO2 concentration(Ci)2.49%-10.68%(P<0.05).Under T2 precipitation type,deep fertilizer application was effective in improving SPAD by 2.92%-4.88%,Pn by10.80%-15.32%,Tr by 3.67%-10.27%,Gs by 15.65%-28.56%,Fv/Fm 1.31%-2.10%,Fv/Fo by 6.83%-9.01%%,Φps II by 6.04%-8.48%,ETR by 6.37%-11.27%,and q N 1.54%-2.30%compared to D5 treatment,and the highest level occurred in D25 treatment(P<0.05).Under T3 precipitation type,D15 treatment significantly increased SPAD by 3.44%-8.66%,Pn by4.44%-9.22%,Tr by 4.27%-12.27%,Gs by 5.08%-14.92%,Fv/Fm by 0.72%-1.64%,Fv/Fo by 5.86%-17.57%,Φps II by 1.41%-3.37%,ETR by 4.86%-10.89%and q N 1.91%-4.65%compared to other deep fertilization treatments(P<0.05).(2)The depth of fertilizer application at different precipitation type had significant effects on canopy photosynthetically effective radiation interception(IPAR),photosynthetically effective radiation interception rate(Ca R),total plant light energy utilization(E_T),light energy utilization of seeds(E_G)and reduced transmittance(Pe K)in winter wheat.Under T1 precipitation type,Ca R,IPAR,ET and EG showed an increasing trend with increasing fertilizer application depth,and D35 treatment significantly increased Ca R,IPAR,ET and EG by 37.21%,33.46%,29.10%and 27.92%,respectively,compared to D5(P<0.05).Under T2 precipitation type,D25 increased Ca R,IPAR,ET and EG by9.84%,13.37%,20.36%and 16.48%,respectively,compared to D5(P<0.05).Under T3precipitation type,D15 treatment increased Ca R,IPAR,ET and EG by 3.15%,2.38%,4.55%and 9.13%compared to D5(P<0.05).(3)Elevated precipitation significantly increased the dry matter mass,leaf area index(LAI)and plant height of winter wheat.The effect of deep fertilizer application on the growth of winter wheat crop was different under different precipitation types.Under T1precipitation type,deep fertilizer application increased aboveground dry matter mass,LAI and plant height of wheat at maturity by 10.12%-26.79%,19.02%-86.11%and8.02%-22.34%,respectively,compared with D5 treatment(P<0.05).Under T2 precipitation type,dry matter mass at maturity was significantly increased by 16.76%、3.76%and 15.65%,LAI by 42.77%、24.24%and 54.23%and plant height by 8.53%、2.70%and 4.33%in the D25 treatment compared to the D5,D15 and D35 treatments,respectively(P<0.05).Under T3 precipitation type,D15 treatment increased dry matter mass at maturity,LAI,and plant height by 5.38%、4.51%and 11.18%compared to D5 treatment,and significantly increased8.68%-20.41%,12.60%-40.12%and 7.90%-13.40%compared to D25 and D35 treatments(P<0.05).(4)Moderate deep fertilizer application under different precipitation types increased aboveground nitrogen accumulation,apparent nitrogen recovery(NRE),nitrogen uptake efficiency(NUPE)and nitrogen production efficiency(NPE)at maturity in winter wheat.Under T1 precipitation type,fertilizer deep application treatment increased aboveground nitrogen accumulation at maturity,NRE,NUPE and NPE of wheat by 13.67%-23.41%、44.81%-76.43%、13.67%-23.41%and 16.10%-27.92%,respectively,compared to D5treatment(P<0.05).Under T2 precipitation type,NRE,NUPE and NPE accumulated significantly increased by 11.01%、42.15%、11.01%and 27.42%,respectively,under D25treatment compared to D5 treatment(P<0.05).Under T3 precipitation type,D15 treatment increased nitrogen accumulation and nitrogen use efficiency by 4.51%、16.46%、4.51%and5.20%compared to D5 treatment(P<0.05).(5)Under T1 precipitation type,D35 significantly increased yield by 27.92%,number of spikes by 12.37%and number of grains by 27.17%compared to D5(P<0.05),but there was no significant difference between thousand grain weight.Under T2 precipitation type,D25 significantly increased yield,number of spikes and number of grains by 27.42%,10.11%and 7.25%,respectively,compared to D5,and 4.88%-16.68%,5.22%-9.55%and3.93%-7.24%,respectively,compared to D15 and D35(P<0.05),with no significant difference between thousand grain weight.Under T3 precipitation type,the four fertilizer depth treatments showed yield and number of spikes and spike number as D15>D5>D25>D35,and D15 treatment increased yield,number of spikes and spike number by 5.20%-16.33%,2.53%-6.62%,and 3.15%-13.91%(P<0.05),respectively,compared with other fertilizer depth treatments,with no significant difference among thousand grain weight.In conclusion,regardless of the rainfall year,appropriate fertilizer deep application can promote wheat growth,improve leaf photosynthetic characteristics and light energy utilization,thus achieving increased yield.In normal years,fertilizer deep application to about 25 cm at the best,in dry years can be appropriate to increase the depth of application(35 cm),in wet years moderately reduce the depth of fertilizer(15 cm).